It is a serious defamatory allegation to accuse a scientist (or pretty well anyone) of being a "Walter Mitty" character and even the swift apology from Tom Kelly, the Downing Street spokesman, would not have deprived Dr Kelly of the possibility of substantial libel damages had he been alive. Sadly his funeral was last week.

But the law of libel is not famous for its chivalry and a defamatory statement about a person who is dead when it is made will not give rise to a valid claim no matter how malicious the person who made it. No 10 has made clear that the comments were part of a general background briefing and not, it is claimed, a spiteful attack upon the deceased.

It is the general rule in civil cases that when the claimant dies, the claim survives for the benefit of the estate. But this is not the case in defamation which, predictably, clings on to a very old common law rule: actio personalis moritur cum persona. That a claim was personal only to the claimants made sense when oral evidence was vital in pre-document and witness-statement days but is rather antiquated now. This leaves Dr Kelly's family with no legal remedy unless (the burden of proof would be on Mrs Kelly) they could show that the statement was known to be false and intended to cause, and did cause, illness to, say, the deceased's widow. And it does not seem ever to have been suggested that No 10 intended to spin against the family rather than the weapons expert.

These old, harsh rules can cause real hardship and can even discourage elderly claimants from commencing actions. But this is not something a newspaper should rely on - Michael Foot, the former Labour leader, already mature in years, took on the Sunday Times and News of the World in 1995 - and won - after allegations by ex-KGB officers. He recently celebrated a libel-free 90th birthday.

When Armand Hammer, a tough businessman from America, who turned Occidental Petroleum into the US's 16th largest industrial corporation, tried to use the law of libel to establish a lasting monument to his good name (despite having been convicted of making a secret $54,000 donation to Richard Nixon's 1972 presidential campaign - he was subsequently pardoned), he finally ran out of gas. He was 90 when in 1988 he sued the publisher Ebury Press over an unflattering book, The Untold Story. But he died in December 1990. The case abated, so Hammer's family had to pay his vast legal costs (which his solicitors had hoped to extract from the publisher had they won) and Random House (which had taken over Ebury Press) was left with huge legal costs which it was not able to even begin to recover. Justice for neither side.

Rather unusually, there is some equality between claimant and defendant in death in libel because it is also the case that no action can be commenced against the estate of a deceased defamer if the person responsible for the libel dies before the verdict. But (and there always is a but) this applies only to the death of an individual. An organisation or person responsible for the deceased can still be involved in the libel though they have lost their star witness.

The untimely death of Robert Maxwell in 1991 meant that his action against American author Seymour Hersh and the publisher Faber and Faber ended. But, unfortunately for the Mirror Group, Maxwell had added his company to many of his claims, which left the newspaper to pay out for his gagging writs as Maxwell had libelled two MPs, Rupert Allason and George Galloway, who had referred to the allegations made by Hersh in parliament (the MPs recovered £230,000 and £150,000 in damages and costs).

The Mirror was also stuck with counterclaims brought by Hersh and Faber and Faber due to articles in the Mirror attacking them. The Mirror was unable to extricate itself from the case until 1994 when it had to shell out further substantial damages and costs.

Journalism is often called the first draft of history but sometimes an author can fail to get the draft absolutely right. When allegations that the dead former prime minister William Gladstone had consorted with prostitutes appeared, members of his family accused the author of lying. He sued, but then faced the difficulty of proving history, thereby providing some sort of comfort to the late politician's family. But this did not mean, of course, that the allegations could not be repeated by others (who did not rise to the family's bait).

When a government spokesperson chats to journalists, it is often easy to assume that any allegations made are covered by qualified privilege but this is not necessarily the case. Protection is given to official documents, formal press releases and press conferences and other information issued for the benefit of the public but the defence of qualified privilege is not there to protect idle chit-chat.

Newspapers taking too seriously what is fed to them by government spokespeople is nothing new. A woman named Carmen Proetta was interviewed in the TV documentary Death on the Rock, which infuriated the Thatcher government by casting doubt on the official version of events after the shooting dead of three suspected IRA terrorists in Gibraltar in 1988. She had given a statement to the police, her recollection being that two of the terrorists had appeared to raise their hands in surrender. Briefings and spinning followed and five newspapers were persuaded that she was a liar and embarked upon a smear campaign.

With newspapers relying in part on whispers from security services, as well as other sources, Proetta was accused of involvement in prostitution, drugs, assault, knowing criminals and Uncle Tom Cobley and all. The Sun was as pro the government position then as some believe it to be now and referred to Proetta as the "Tart of Gibraltar". Apologies, costs and very substantial damages (estimated at £350,000) followed. The newspapers were unable to justify the allegations they had published as the semi-official sources dried up. Fleet Street's finest were confronted, with little admissible or relevant evidence to help them, with a claimant who was very much alive.

Dr Kelly's family will now have to rebuild their lives but it is unlikely that the law of libel will provide them with a platform to vindicate the reputation of the deceased.

Perhaps we all need to be reminded that the fact that a government spokesperson says something, or indeed a newspaper publishes it, does not necessary make it true. And a live claimant can make those responsible for the publication of slurs very sorry indeed.

· Duncan Lamont is a media partner at City solicitors Charles Russell

Back to the source

The question of confidentiality of journalistic sources is something that the average man or woman in the street finds very difficult to understand. Why is it a life-and-death matter if a journalist - as with Andrew Gilligan and Dr David Kelly - is not prepared to reveal his or her source on a particular story? Even when Kelly came forward and admitted that he had spoken to Gilligan, the reporter still would not admit if he was the source or not. It was only after Kelly's body was found that Gilligan admitted he was the source. Many, including the NUJ, argue that the BBC was wrong to admit Kelly was the source even after his death. The union claims journalistic confidentiality is sacrosanct; that breaking it will make other journalists' jobs impossible and in situations like Northern Ireland put lives at risk.

The confidentiality question has not surprisingly arisen in many guises in Northern Ireland. Four years ago, Ed Moloney refused to disclose his notes of an interview with the Loyalist paramilitary William Stobie, who had supplied the guns used to murder Catholic solicitor Pat Finucane in 1989. More recently Alex Thomson and Lena Ferguson, both Channel 4 News journalists, have refused a request from the Bloody Sunday tribunal to name soldiers they interviewed or hand over original notes that would identify them. When threatened with contempt-of-court proceedings, Thomson stated that he would go to jail before revealing his sources. The opposite approach was taken by Nick Martin Clark. Interviewed by him in prison, the Loyalist paramilitary Clifford McKeown admitted he had murdered a Catholic taxi driver.

McKeown swore Martin Clark to secrecy but the journalist felt he could not live knowing such a secret; he published his story in the Sunday Times and gave evidence against McKeown in court. McKeown was subsequently convicted of murder and sentenced to 24 years in prison. Martin Clark, who angered the NUJ by breaking its confidentiality rule, is now under the witness protection scheme and claims to have received death threats.

For the likes of Alastair Campbell, whose aim in life is to control information flow, the power to force the revelation of sources would make life easier. Potential whistleblowers would be reluctant to approach journalists, not knowing if they were going to be exposed at some later date. The fallout from the Kelly and Martin Clark cases shows just how damaging and dangerous revealing sources can be for the sources themselves and the journalists. In the public interest, journalistic confidentiality must be protected - failure to do so would be the first step to a totalitarian society. Paul Donovan